In conventional practice, there are air-conditioning apparatuses comprising a heat source unit, a usage unit, and a communication pipe for connecting the heat source unit and the usage unit. With this type of air-conditioning apparatus, a method is used in which the heat source unit is charged in advance with a predetermined amount of refrigerant, and when the apparatus is installed on site, it is charged with an additional amount of refrigerant according to the length of the communication pipe connecting the heat source unit and the usage unit. However, since the length of the refrigerant pipe differs depending on the conditions of installing the air-conditioning apparatus at the installation site, there have been cases in which it is difficult to charge the refrigerant circuit with an appropriate amount of refrigerant.
In view of this, an operation has been proposed in which, when the refrigerant circuit is additionally charged with refrigerant, the amount thereof is determined according to the degree of subcooling of the refrigerant in the outlet of a heat source-side heat exchanger functioning as a condenser while the usage unit is set to the cooling operation, and the refrigerant continues to be charged until the degree of subcooling reaches a predetermined value (Japanese Laid-open Patent Application No. 2006-23072, for example).